Centralized traffic controlling system for railroads



June 1, 1937. N. D. PRESTON CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Filed Aug. 18, 1933 2 Sheets-Sheet 1 INVENTOR MM mv v p Hu 558m .53m 41 56" 2F L 22m T1 3 5 6 E u u u u n .llll'lllL FIIIIIL June 1, 1937.

N. D. PRESTON GENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Filed Aug. 18, 1953 2 Sheets-Sheet 2 v T4 3 m "0U 58 2% Patented June 1, 1937 UNITED STATES FATE GFFIQE CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Application August 18, 1933, Serial No. 685,764

, 18 Claims.

This invention relates to centralized traffic controlling systems for railroads and it more particularly pertains to the communication part of such systems.

The present invention contemplates a centralized traflic controlling system in which the switches and signals at a plurality of stations located along a railroad track are connected to the control ofilce by means of a communication line circuit. The switches and signals at the stations are under the supervision of an operator at the control office so that the condition of such switches, signals and Various other traffic controlling devices at the distant locations can be transmitted to the control oflice for providing the operator with the necessary information for governing train movements. In a system of this type, the switches and signals are associated with the usual automatic block arrangements and such other local means as are ordinarily provided to guard against unsafe train movements, improper operation of track switches or the like.

The switches and signals at the stations are governed over the communication line circuit so that the operator in the control office can position the switches to normal and reverse, as well as clear the proper signals for trafiic to proceed, subject to the usual lock circuits which prevent the improper operation of a switch or the clearing of a wrong signal.

Either control impulses are transmitted from the control office or indication impulses are transmitted from a field station during an operating cycle for controlling the various switches, signals and indicating devices at the distant location. The impulses for the purpose of transmitting controls are made distinctive by reason of their polarity. The impulses for the transmission of indications may also be made distinctive by reason of their polarity or by any other desirable method of impulse transmission. Since the present invention does not relate to the manner in which these impulses are governed or trans mitted and since the control ofilce circuits are immaterial to an understanding of the present invention, only that part of a typical field station is illustrated which relates to the contemplated invention.

In a centralized traffic controlling system employing a coded type of communication system ing in synchronism with a similar step-by-step mechanism in the control ofiice.

The present invention proposes a step-by-step mechanism for coded type systems in which a bank of stepping relays selects a plurality of local 5 control circuits. This bank of stepping relays likewise selects a plurality of local indication circuits but since this portion of the communication system to which the invention is applied is immaterial to an understanding of the present disclosure, the indication circuits have been omitted.

It is desirable in a coded type of communication system to provide a checking means at the field stations to guard against the stepping relay bank at a field station taking an improper number of steps in response to the stepping impulses. A feature of the present invention relates to making a check of the field station stepping relay operation and if an improper number of impulses has been received, the controls received during an operating cycle are canceled at the end of this cycle.

Other objects, purposes and characteristic features of the present invention together with the advantages and functions of the present system will be in part pointed out and in part apparent as the description progresses.

In describing the invention in detail, reference will be made to the accompanying drawings which illustrate one method of carrying out the invention by way of example. The drawings illustrate in a diagrammatic manner the apparatus and circuits employed and for convenience in describing the invention in detail, those parts having similar features and functions are designated by like reference characters generally made distinctive by the use of suitable preceding numerals representative of the order of their operation and in which:

Fig. 1 illustrates a portion of the apparatus and circuits employed at a typical field station.

Fig. 2 illustrates an additional portion of the apparatus and circuits employed at the same typical field station.

The illustrations in the drawings are schematic and abbreviated for the purpose of clearness and simplicity. The arrangement of those parts of a centralized traffic controlling system which are not illustrated in the drawings and their cooperation and connection with the illus- 5O trated portions will be set forth in the following general description.- After the general description, a detailed description will be given of the reception of controls from the control ofiice for operating the various control devices and for canceling the functioning of these devices under certain conditions.

General description The symbols and are employed to indicate the positive and negative terminals respectively of suitable batteries or other sources of direct current and the circuits with which these symbols are used always have current flowing in the same direction.

While the features of the invention are ap-- plicable to and usable with any type of communication system for centralized traflic control, the specific embodiment has been shown in a form adapted for use with a selective communication system of the coded type shown and described in detail in the pending application of T. J. Judge, Ser. No. 652,176, filed January 17, 1933. Therefore, before considering the structure and mode of operation of the parts constituting this invention it is desirable to explain some of the features of the communication system insofar as material to an understanding of the present invention, reference being made to said prior application for other details of the structure and operation of such a system not directly related to the features of this invention.

The field stations are connected to the control oflice over a two-wire communication line circuit including conductors I 0 and II as illustrated in the upper left hand portion of Fig. 1. The line relays such as relay F at the various field stations are all connected in series in line conductor ID, for example.

At the control oifice, a linebattery is provided and arranged for being selectively connected to the line circuit so that impulses of and polarity are impressed on the line for conditioning the various line relays. It will be understood that the control oflice battery supplies current for energizing the line circuit during the transmission of controls and that the two line conductors i2 and I3 which extend through the other field stations are connected together at the end station for providing a closed two-wire circuit which may be energized by the control ofiice battery.

In the above mentioned prior application Ser. No. 652,176, a line battery is located at each field station for the purpose of transmitting inbound calls to the control oifice but since the present invention is not concerned with this portion of the operation of the system, the field station line battery has been omitted from the present drawmgs.

Description of apparatus With reference to Fig. 1 of the accompanying drawings, the step-by-step apparatus at the typical field station is illustrated as controlled over a line circuit which includes a line wire I0 and a three-position biased-to-neutral polarized line relay F. It will be assumed that different series of impulses are placed upon this line circuit in the control ofiice for causing the step-by-step operation at the several stations irrespective of the polarity of the impulses, while the polarity of the impulses of a series forms the code call for the desired station and the controls to be transmitted to that station. The line relay F is provided with polar contacts 2 and 3 which are operated to right hand positions by a impulse over the line circuit and to left hand positions by a impulse over the line circuit.

A quick acting line repeating relay FP repeats each energization of line relay F irrespective of the polarity of such energization, by reason of the closure of an energizing circuit by contact 2 of relay F in either its right or left hand dotted positions.

A slow acting relay SA is energized each time relay FF is picked up by reason of the closure of front contact 4 of relay FP. Relay SA is slow in picking up and slow in dropping away. This arrangement provides that relay SA is picked up at the beginning of each series of impulses and remains up throughout the cycle irrespective of the time spaces between successive impulses, but it drops at the end of the cycle when the line circuit has been deenergized for a predetermined period of time.

A slow acting relay SAP repeats each energization of slow acting relay SA. Relay SAP is picked up at the beginning of each cycle of operations by reason of the closure of front contact 5 of relay SA. Relay SAP is slow in picking up and slow in dropping away so that this relay likewise provides an additional time interval at the end of each cycle before the circuits are restored completely to normal, even after the dropping of relay SA.

The field station includes a lock-out relay LO which is picked up at that field station which is sending indications over the communication line. This portion of the operation of the system is immaterial to an understanding of the present invention, except that the back contacts shown associated with relay LO indicate that the control circuits are ineffective at a field station which is transmitting indications to the control office. Since lock-out relay L0 is deenergized during a control cycle, these two back contacts are closed so that the control circuits are completed. The circuit operation of the look-out feature controlled by relay LO may be the same as in the above mentioned prior application Ser. No. 652,176.

A stepping relay bank including stepping relays IV, 2V, 3V, 4V and LV together with the associated half step relay VP is provided. These relays operate in synchronism with corresponding relays in the control oifice so that the stepping relays take one step for each deenergization of the line as controlled by back contact 6 of relay FP.

A pilot relay bank including relays IPT and 2PT together with a station relay ST are provided to effect station selection. It is assumed that station selection is effected by the selective conditioning of the two pilot relays IPT and ZPT by the two impulses applied to the line, one after each of the first two stepping relays IV and 2V take their steps. It will be understood that additional pilot relays may be provided and connected in an obvious manner as the size of the system demands.

For the purpose of illustrating the reception and the cancellation of controls as contemplated by the present invention, right direction control relay RD and left direction control relay LD are illustrated in Fig. 2. These two relays are selectively conditioned by the impulse follow ing the picking up of relay 3V.

These control relays function to clear the signals over the track switch TS. Additional switch control relays are ordinarily provided (not shown) to cooperate with these direction control relays for controlling the operation of the switch machine. The complete operation of a system of control relays for operating the track switch and clearing the signals may be as completely disclosed in the prior application of T. J. Judge, Ser. No. 678,045 filed June 28, 1933.

Associated with track switch TS is the usual normally energized track relay T and its normally energized repeating relay TP. Stop relay S has a back contact included in the stick circuit of relays RD and LD. The operation of this stop relay may be controlled in the same manner as disclosed for example in the above mentioned Judge application Ser. No. 678,045 when modified by controlling the stop relay with the opposite code characteristics of a particular step succeeding the control step for relays RD and LD, instead of like code characteristics of the two successive steps which control relays RD and LD in said prior application.

Executing relay EX is provided to energize the signals or other controlled devices at the end of an operating cycle, only when the proper number of steps have been taken at the associated field station.

It is believed that the nature of the invention, its advantages and characteristic features may be best understood with further description being set forth from the standpoint of operation.

Operation While the system is at rest or in its so-called period of blank, the line circuit including line wires iii and II is normally deenergized. The relays and circuits of the system are normally deenergized, with a few exceptions. For example, track relay T (Fig. 2) is normally energized over the usual circuit including the track battery, when the track is in its unoccupied condition. Track repeating relay TP is normally energized over a circuit extending from front contact IOI of relay T and winding of relay TP, to Executing relay EX is normally energized over its stick circuit extending from back contact I4 of relay SA, conductor I5, front contact I82 and winding of relay EX, to

It will now be assumed that a series of time spaced impulses placed upon the line circuit in the control office includes five energized periods, the first or conditioning period being relatively longer than the rest. Also, the last energized period of the line circuit is followed by a relatively long deenergized period before another series of impulses is applied to the line circuit. The polarity of these impulses may be determined in accordance with the usual means provided in such a coded type system. The particular code arrangement is immaterial for an understanding of the present invention, except that it should be understood that each impulse may be either positive or negative in character and such distinctive character is effective to position line relay F to the right and to the left respectively.

Step-by-step operatio-1z.-The application of the first impulse to the line energizes relay F and irrespective of the polarity of this impulse relay FF is energized by the closure of contact 2 in either a right or a left hand position. The energization of relay FP closes its front contact 4 which energizes relay SA and since the first or conditioning impulse of the series is relatively long, sufficient time is provided for the contacts of relay SA to pick up. The closure of front contact 5 of relay SA energizes relay SAP and since the first energized period of the line circuit is of long duration, sufficient time is provided for relay SAP to pick up its contacts. During the deenergized periods of the line circuit and the resulting dropping of relay PP, relays SA and SAP remain in their picked up positions due to the slow acting characteristics of these relays.

As soon as relay SAP closes its front contact 1, a circuit is closed for picking up relay VP which extends from front contact I of relay SAP, front contact 8 of relay FP, back contacts 9, 20, 2|, 22 and 23 of relays LV, 4V, 3V, 2V and IV respectively and the winding of relay VP, to

As soon as relay VP picks up, its temporary stick circuit is closed including the above described pick-up circuit by way of front contact 24 of relay VP, which contact bridges front contact 8 of relay FP. It is apparent that this stick circuit will remain closed until the first stepping relay IV is picked up.

Upon the deenergizaticn of relay FP for the first time space in the series of impulses, a holding stick circuit is closed for relay VP extending from front contact 1 of relay SAP, back contact 8 of relay FP, front contact I6 and winding of relay VP, to

The dropping of relay FP at the start of the first deenergized period of the series of impulses closes a pick-up circuit for relay IV extending from front contact I! of relay SAP, back contact 6 of relay PP, front contact l8 of relay VP, back contact I9 of relay 4V, back contact 25of relay 2V and winding of relay IV, to Relay IV closes a stick circuit for itself from at front contact ll of relay SAP by way of front contact 26 of relay iV.

Upon the next energization of the relay FP in response to the second impulse applied to the line circuit, relay VP is deenergized by back contact 8 of relay FP opening the holding stick circuit of relay VP. Since the above described pick-up circuit of relay VP is now open at back contact 23 of relay IV, relay VP drops.

Upon the next deenergization of relay FPHin response to the second time space in the series of impulses, relay FP closes a pick-up circuit for relay 2V extending from .front contact ll of relay SAP, back contact 6 of relay FP, back contact I8 of relay VP, back contact 21 of relay 3V, front contact 28 of relay IV and Winding of relay 2V, to Relay 2V closes an obvious stick circuit for itself by way of its front contact 29.

Upon the next energization of relay FP in re- 9, and 2| of relays LV, 4V and 3V respectively,

front contact 22 of relay 2V and winding of relay VP, to The previously described temporary stick circuit for relay VP is established through front contact 24 of relay VP and the remainder of the circuit just described.

Upon the next deenergization of relay FP in response to the third time space in the series of impulses, the previously described holding stick circuit (including front contact 56) is established for relay VP. Relay 3V is picked up at this time over a circuit extending from front contact I! of relay SAP, back contact 5 of relay FP, front contact I8 of relay VP, back contact I9 of relay 4V, front contact of relay 2V and winding of relay 3V, to Relay 3V closes an obvious stick circuit for itself by way of its front contact 30.

Upon the next energization of relay FP in response to the fourth impulse applied to the line circuit, relay VP is deenergized because its holding stick circuit is opened at back contact 8 of relay FP and its pick-up circuit is open at back contact 2| of relay 3V.

Upon the next deenergization of relay FP in response to the fourth time space, a pick-up circuit is closed for relay 4V extending from front contact I! of relay SAP, back contact 6 of relay FP, back contact l8 of relay VP, front contact 21 of relay 3V and winding of relay 4V, to Relay 4V closes an obvious stick circuit for itself by way of its front contact 3|.

Upon the next energization of relay FP in response to the fifth impulse applied to the line circuit, relay VP is picked up over a circuit extending from front contact I of relay SAP, front contact 8 of relay FP, back contact 9 of relay LV, front contact 20 of relay 4V and winding of relay VP, to The previously described temporary stick circuit of relay VP is established through its own front contact 24 and the remainder of the circuit just described.

Upon the next deenergization of relay FP in response to the beginning of the last (long) time space, a pick-up circuit is closed for relay LV extending from front contact I! of relay SAP, back contact 6 of relay FP, front contact I8 of relay VP, front contact 19 of relay 4V and winding of relay LV, to Relay LV closes an obvious stick circuit for itself by way of its front contact 32.

From the above description it will be observed that the stepping relays are picked up in rotation during successive deenergized periods of the line circuit and that the half step relay VP is shifted during successive energized periods of the line circuit. It will be understood that the same method of operation may be carried out for as many steps as desired, with the pick-up and stick circuits of additional stepping relays and the half step: relay arranged in the manner disclosed in connection with the stepping relays illustrated in Fig. 1.

End of operating cycZe.--The control office circuits are so arranged that the last deenergized period of the line circuit is comparatively long which allows relays SA and SAP of Fig. 1 to be released. The manner of accomplishing this is immaterial to the present invention. For example, the circuits may be arranged to accomplish this result in the manner disclosed in the above mentioned prior application Ser. No. 652,176.

The dropping of contact I! of relay SAP deenergizes the stick circuits of the stepping relays and these relays are dropped. The dropping of front contact 1 of relay SAP deenergizes the stick circuit of relay VP allowing this relay to drop. The dropping of front contact 33 of relay SAP deenergizes the stick circuit of the pilot relay or pilot relays picked up during the cycle (as will be later described) and the pilot relays are restored to normal.

Reception of polar z'mpuZses.It will now be assumed that the station illustrated in Figs. 1 and 2 responds to code combination on the second and third steps of the cycle and that relay ST is picked up after these steps are taken for selecting this station as the one to which controls are to be transmitted during succeeding steps of the cycle.

In this event, the control oflice applies a positive impulse to the line circuit during the secnd and third energized periods, following the conditioning or first energized period. It will be understood that the conditioning energized period is for the purpose of conditioning the slow acting relays and that no stepping relay is picked up during this period. The half step relay is picked up however during the conditioning period as previously described.

Assuming that relay IV is picked up during the first time space as above described and that the second impulse applied to the line is relay F is actuated to its right hand dotted position closing a circuit for picking up relay IPT. This circuit extends from back contact 34 of relay LO, front contact 35 of relay SAP, contact 3 of relay F in its right hand dotted position, back contacts 36, 3'! and 38 of relays 4V, 3V and 2V respectively, front contact 39 of relay IV and lower winding of relay IPT, to Relay IPT closes an obvious stick circuit for itself by way of its front contact 40.

The third impulse applied to the control line is assumed to be and since relay 2V is picked up during the second time space just preceding this impulse, a circuit is closed for picking up relay 2PT. This circuit is the same as previously described for relay lPT except that it extends through front contact 38 of relay 2V and lower Winding of relay 2PT, to Relay ZPT closes an obvious stick circuit for itself by way of its front contact 4|.

When stepping relay 3V is picked up during the third time space, a circuit is closed for energizing station relay ST which extends from at the right hand terminal of the winding of relay 3V (either by way of the pick-up circuit or the stick circuit for relay 3V), back contact 42 of relay LO, front contact 43 of relay ZPT, front contact 44 of relay lPT and winding of relay ST, to Relay ST remains picked up until relay SAP is dropped at the end of the cycle to deenergize the stick circuits of the stepping relays and the pilot relays.

While a selection of only four stations is possible with two station selecting steps as indicated in Fig. 1, it will be understood that additional stations may be selected by providing additional pilot relays selected through additional circuits of higher numbered stepping relays. It will also be understood that impulses applied to the line circuit during the station selecting steps position relay F to the left, thus preventing the picking up of the pilot relays illustrated in Fig. 1. These two impulses do however pick up similar pilot relays at the station which has a code. Thus the combination of the first two impulses results in the selection of one out of four stations by picking up the station relay only at one selected station.

Assuming the station of Fig. 1 selected, then upon the next energization of relay F in response to the fourth impulse applied to the line circuit, right direction relay RD or left direction relay LD will be energized depending upon the polarity of this impulse. If the fourth impulse is relay LD is picked up over a circuit extending from back contact 34 of relay LO, front contacts 35 of relay SAP, contact 3 of relay F in its right hand dotted position, back contact 36 of relay 4V, front contact 31 of relay 3V, front contact 45 of relay ST, conductor 46, back contact 41 of relay RD and lower winding of relay LD, to If the fourth impulse is a circuit is closed for picking up relay RD extending from back contact 34 of relay LO, front contact 35 of relay SAP, contact 3 of relay F in its left hand dotted position, back contact 48 of relay 4V, front contact 49 of relay 3V, front contact 50 of relay ST, conductor 5|, back contact 52 of relay LD and lower winding of relay RD, to

Either relay LD or relay RD picking up as above described closes a stick circuit for itself including its front contact 53 (of relay LD) or front contact 54 (of relay RD), back contact 55 of relay S, front contact 56 of relay T, conductor 51 and front contact 58 of relay SA, to The operation of one of these direction relays may control any suitable signal, for example, the direction signals associated with track switch TS by means of circuits indicated by dotted line 59. Since the circuits controlled by relays LD and RD are immaterial to an understanding of the present invention, they have not been shown in detail but for the sake of simplicity have only been indicated by dotted line 59. Of course, the local. signals or other devices controlled by relays LD and RD may be organized in any suitable manner to meet trafiic requirements and may be subject to suitable switch lock, approach locking and other desired safety requirements.

Execution of cntr0Zs.Since an important feature of the present invention relates to the canceling or annuling of control conditions received at a field station in the event of an improper number of impulses, it is necessary to delay the execution of the controls after they have been recorded until the end of the cycle is reached when a check is made to determine if the proper number of impulses has been recorded.

It will first be assumed that the proper number of impulses was received during the operating cycle previously described. At the beginning of the cycle, relay SA picks up its back contact I4 which deenergizes the stick circuit of relay EX, allowing this relay to: drop its contacts. The dropping of front contact 60 of relay EX deenergizes the circuit leading to front contacts BI and 62 of relays RD and LD respectively so that even though one or the other of these relays is picked up, energizing circuits are not completed to the signal or other circuits which they control.

When relay LV is picked up at the beginning of the last deenergized period as above described, it closes its front contact 63. When relay SAP is dropped at the end of the cycle it closes a circuit for picking up relay EX extending from back contact 54 of relay SAP, front contact 63 of relay LV, conductor 65 and winding of relay EX, to Relay EX closes a stick circuit for itself which is now completed from back contact M of relay SA, conductor l5, front contact I02 and winding of relay EX, to

With relays LV and VP energized, potential is applied to conductor 51 through front contact 65 of relay LV and front contact G'l of relay VP. This potential on conductor 51 maintains the stick circuit for relays LD and RD energized until relay SAP drops its back contact 68. The closure of back contact 68 also energizes this stick circuit so that the dropping of contacts 61 and 65 of relays VP and LV (after back contact 68 is closed) do not interrupt the stick circuit for the control relays LD and RD when the proper number of steps has been taken.

The direction relay which is energized now remains stuck up until the track section is occupied or until a stop code is received. Track occupancy drops relay T which interrupts the stick circuit of the direction relays at front contact 56. Shortly after relay T is dropped, relay TP drops its back contact 69 to again complete this stick circuit. This allows the stick circuit of the control relay to be momentarily deenergized, allowing the control relay to drop and shortly thereafter this stick circuit is again energized so that the control relay may be stuck up if picked up on a succeeding cycle while the detector track section is still occupied. Stop relay 5 may also be picked up in response to a control transmitted from the control office for deenergizing the stick circuit of the direction relays. This provides an automatic control of the direction relay stick circuit as well as a manual control from the control ofiice.

Since relay EX is picked up at the end of the cycle and stuck up as long as relay RD has its front contact iii closed or relay LD has its front contact '55 closed, the signal controlling circuits are completed through front contact 50 of relay EX and either front contact 6| of relay RD or front contact 52 of relay LD, depending upon which one of these relays is picked up. From the above it will be noted that even though a succeeding cycle is initiated and back contact i l of relay SA is picked up, the stick circuit of relay EX is maintained energized at either front contact H3 or front contact H until both relays RD and ID are dropped.

It will now be assumed that the stepping relay bank misses one or more steps so that relay LV is not picked up when the last time space is initiated as above described. This results in conductor 5! being deenergized when relay SA drops its front contact 58, during the time interval between the dropping of contact 58 and the dropping of back contact 58 of relay SAP. It will be obvious that relay ST at this particular station is picked up so that its back contact '82 does not energize conductor 51.

With conductor 57 deenergized at the end of the cycle, the stick circuit for the LD and RD relays is deenergized so that both of these relays will be down and the circuits controlled through their contacts 6! and 52 will be incomplete. It is necessary for another cycle of operations to take place before relay LD or relay RD can be again picked up.

It will now be assumed that relay LV is picked up at the beginning of the last deenergized period of the line circuit as previously described and it will be assumed that an additional impulse is applied to the line for some reason. This impulse picks up relay F"? and deenergizes the holding stick circuit of relay VP at back contact 8. Since back contact 9 of relay .LV is picked up, the circuit of relay VP is open so that it is dropped and its front contact 51 is opened.

This results in deenergizing conductor 57 at front contact 6! of relay VP so that the stick circuit of relay LD and RD is deenergized. This effects the release of these relays before relay EX picks up its front contact 58 at the end of the cycle. Therefore, the circuits to the signals or other devices are incomplete.

In the event that more than one additional impulse is received, relay VP remains down while relay LV is up and conductor 51 is momentarily deenergized at the end of the cycle for dropping the direction relay that was picked up during the cycle.

It will be understood that front contacts 38 and 48 of relay 4V (and other similar contacts on other stepping relays when provided) connect through front contacts of relay ST to additional control relays similar to relays LD and RD. The

final circuits which these additional control relays energize would then be controlled in the manner illustrated bycontacts 60, 6| and 62 of relays EX, RD and LD respectively.

It will be understood that back contact I2 of relay ST energizes conductor 51 in order that a control relay such as RD or LD which is stuck up at a non-selected station (relay ST not picked up) cannot be dropped, irrespective of the removal of from conductor 51 by contacts 58, 68, 66 and S1 at such non-selected station.

Having thus described one specific embodiment of a centralized trafiic controlling system, it is desired to be understood that the particular arrangement illustratedis only typical of applicants invention and is not intended to illustrate the exact circuit design necessary for carrying out the features of the invention but this form has been selected to facilitate in the disclosure rather than to limit the number of forms which it may assume and it is further desired to be understood that various modifications, alterations and adaptations may be made in order to meet the various problems encountered in practice and the system may be varied in the number of field stations to which the invention is applied and the number of circuits controlled at a particular field station, all without in any manner departing from the spirit or scope of the present invention except as limited by the appended claims.

What I claim is:

1. In a centralized trafiic controlling system for railroads, a line circuit having different code combinations applied thereto, each comprising same number of code impulses, a field station, signals at said station, a plurality of control relays for selectively energizing said signals, a station relay for selecting said control relays, means controlled by said code combinations for selectively actuating said control relays, and means for maintaining said control relays actuated until a subsequent code combination, when once actuated, only when the number of impulses in said code combination equals said number.

2. In a centralized traflic controlling system for railroads, a line circuit having a distinctive number of impulses of distinctive character applied thereto during a cycle of operations, a field station, signals at said station, control relays picked up during said cycle in accordance with the character of said impulses for selecting said signals, an executing relay picked up during said cycle for energizing said selected signals, and a stick circuit for said executing relay controlled by said control relays.

3. In a centralized trailic controlling system for railroads, a line circuit having a distinctive number of impulses of distinctive character applied thereto during a cycle of operations, a field station, signals at said station, control relays picked up during said cycle in accordance with the character of said impulses for selecting said signals, an executing relay picked up during said cycle for energizing said selected signals,

a stick circuit for said executing relay controlled by said control relays, and a stick circuit for said control relays controlled in accordance with the number of said impulses.

4. In a centralized traffic controlling system for railroads, a line circuit having a predetermined number of impulses of distinctive character applied thereto during a cycle of operations, a field station, signals at said station, a track relay for indicating occupancy of a track section at said station, control relays picked up during said cycle in accordance with the character of said impulses for selecting said signals, an executing relay picked up during said cycle for energizing said selected signals, a stick circuit for said executing relay controlled by said control relays, and a stick circuit for said control relays controlled in accordance with the number of said impulses and the position of said track relay.

5. In combination with a section of railway track, a track circuit for said section including a track relay, a signal for governing trafiic through said section, a remotely controlled selector, a control relay for said signal, means including said selector responsive to remote control for momentarily energizing said control relay, means controlled by said track relay for subsequently energizing a holding circuit for maintaining the control relay in its energized condition, means controlled by said selector when it takes an improper number of steps in response to said remote control for momentarily deenergizing said holding circuit, and means controlled by said control relay for governing the associated signal.

6. In combination with a section of railway track, a track circuit for said section including a track relay, a pair of opposing signals for governing traffic in opposite directions through said section, a remotely controlled selector, a pair of control relays one for each of said signals, means including said selector responsive to remote control for selectively momentarily energizing said control relays, means controlled by said track relay for subsequently energizing a holding circuit for maintaining the selected control relay in its energized condition, means responsive to an overstep or an under-step of said selector operating in response to said remote control for momentarily deenergizing said holding circuit, and means controlled by each control relay for governing the associated signal.

7. In combination with a section of railway track, a signal for governing traffic over said section, a track circuit for said section including a track relay, a remotely controlled selector associated with said section responsive to a number of impulses of distinctive character received from a remote location, a control relay and an executing relay associated with said selector, means controlled by an impulse of distinctive character received by said selector for momentarily energizing said control relay, means controlled by a predetermined number of impulses received by said selector for momentarily energizing said executing relay, a stick circuit for said executing relay including a front contact of said control relay, a stick circuit for said control relay including a front contact of said track relay, means responsive to a number of impulses different from said predetermined number for deenergizing the stick circuit of said executing relay, and means for clearing said signal only when said control relay and said executing relay are both energized.

8. In a remote control system, a line circuit having a definite total number of impulses of distinctive character applied thereto to comprise a series of coded impulses, a field station, signals at said station, a control relay for governing said signals, a pick up circuit for said relay energized in accordance with the character of said coded impulses, and a stick circuit for said relay energized in accordance with the definite total number of said coded impulses.

9. In a remote control system, a line circuit having a plurality of code combinations applied thereto each comprising the same number of impulses of distinctive character, a field station, signals at said station, a plurality of control relays for governing said signals, pick up circuits for said relays each selectively energized in accordance with the character of said impulses of its particular one of said code combinations, and a stick circuit for said relays maintained continuously energized when and only when the number of impulses in each code is. said number.

10. In a remote control system, a line circuit having a distinctive number of impulses of distinctive character applied thereto during a cycle of operations, a plurality of field stations, signals at each of said stations, control relays for governing said signals and actuated in accordance with the character of said impulses, a station selecting relay at each of said stations for selecting the corresponding one of said stations, means at a selected station controlled by said distinctive number of impulses for maintaining said control relays actuated when once actuated during said cycle, and means at a non-selected station independent of the number of said impulses for maintaining said control relays actuated when once actuated during said cycle.

11. In a remote control system; a line circuit having dilTerent code combinations applied thereto, each code combination comprising a predetermined number of distinctive current impulses; a device; a neutral control relay for governing the operation of said device; a pick-up circuit for said neutral control relay energized momentarily when a particular one of said code combinations is applied-to said line circuit; a stick circuit for said neutral control relay energized as soon as said neutral control relay is picked up and maintained energized until another particular one of said code combinations is applied to said line circuit; and means for momentarily deenergizing said stick circuit at the end of said one particular code combination if the number of impulses in such code combination is other than said predetermined number.

12. In combination; a section of railway track; a track circuit for said section including a track relay; a signal for governing trailic through said section; a control relay for clearing said signal when it is picked up; a remotely controlled selector; a pick up circuit for said control relay at times momentarily energized by said selector; a slow acting relay repeating said track relay; a stick circuit for said control relay including a front contact of said track relay and a back'con tact of said repeater relay in multiple; and means controlled by the said selector when it has taken an improper number of steps for momentarily opening said stick circuit.

13. In combination, a section of railway track, a track circuit for said section including a track relay, a signal for governing traffic through said section, a control relay for clearing said signal when it is picked up, a remotely controlled selector including a series of stepping relays responsive to take one step for each of a series of code impulses received over a line circuit, a pick up circuit for said control relay momentarily energized by said I selector upon the reception of a particular code, a slow acting relay repeating said track relay, a stick circuit for said control relay including a front contact of said track relay and a back contact of said repeater relay in multiple, and means responsive to an over-step or an under-step of said series of stepping relays and efiective upon the completion of said particular code to momentarily open said stick circuit.

14. In a remote control system, a line circuit having a series, of time spaced impulses applied thereto, a line relay responsive to each impulse of said series, a slow acting relay controlled by said line relay so as to be picked up at the beginning of each series and dropped at the end ofv each' series, a slow acting repeater relay for said slow acting relay, a, step-by-step means controlled by said line relay to take one step for each of said impulses so as to successively close local channel circuits for each step, a bus wire, circuit means including a front contact of said slow actrelay and a back contact of said slow acting repeater relay multiple for applying energy to said bus wire, circuit means for applying energy to said bus wire at the end of said series of impulses and until said slow acting repeater relay is dropped away only if said step-by-step means has taken the proper number of steps, and electro-responsive means momentarily controlled through the medium of said local channel circuits and maintained controlled dependent upon energy from said bus wire.

15. In a remote control system, a line circuit having a series of time spaced positive and/or negative impulses selectively applied thereto, a line relay responsive to the polar characteristic of each impulse of said series, a slow acting relay controlled by said line relay so as to be picked up at the beginning of said series and dropped at the end of such series, a slow acting repeater relay for said slow acting relay, a stepby-step means controlled by said line relay to take one step for each of said impulses so as to successively close local channel circuits for each step, a bus wire, circuit means including a front contact of said slow acting relay and a back contact of said slow acting repeater relay in multiple for applying energy to said bus wire, circuit means for also applying energy to said bus wire at the end of said series of impulses and until after said slow acting repeater relay is dropped away, said means being effective only if said step-by-step means has taken the proper number of steps, pairs of neutral relays for each of said steps, means including said local channel circuits and said line relay for energizing one or the other of said neutral relays for each step depending upon whether the impulse for that step is positive or negative, and stick circuit means for each of said neutral relays including its own front contact and receiving energy from said bus wire, whereby any of said neutral relays picked up during said series of impulses are dropped away at the end of such series unless the proper number of steps has been taken bysaid step-by-step means.

16. In a remote control system, a line circuit having a series of time spaced positive and/or negative impulses selectively applied thereto, a line relay responsive to the polar characteristic of each impulse of said series, a slow acting relay controlled by said line relay so as to be picked up at the beginning of said series and dropped at the end of such series, a slow acting repeater relay for said slow acting relay, a step-by-step means controlled by said line relay to take one step for each of said impulses so as to successively close local channel circuits for each step, a bus wire, circuit means including a front contact of said slow acting relay and a back contact of said slow acting repeater relay in multiple for applying energy to said bus wire, circuit means for also applying energy to said bus wire at the end of said series of impulses and until after said slow acting repeater relay is dropped away, said means being effective only if said stepby-step means has taken the proper number of steps, pairs of neutral relays for each of said steps, means including said local Channel circuits and said line relay for energizing one or the other of said neutral relays for each step depending upon whether the impulse for that step is positive or negative, and stick circuit means for each of said neutral relays in cluding its own front contact and receiving energy from said bus wire, whereby any of said neutral relays picked up during said series of impulses are dropped away at the end of such series unless the proper number of steps has been taken by said step-by-step means, a neutral executing relay, a pick up circuit closed for said executing relay momentarily at the end of said series of impulses after said slow acting repeater relay has dropped away, a stick circuit for said executing relay closed only providing at least one of said neutral relays remains picked up, and control circuits selectively controlled by said neutral relays only provided said executing relay remains picked up.

1'7. In a remote control system, a line circuit having different series of time spaced positive and/or negative impulses selectively applied thereto, a line relay responsive to the polar characteristic of each impulse of each of said series, a slow acting relay controlled by said line relay so as to be picked up at the beginning of each of said series of impulses and dropped at the end of each such series, a slow acting repeater relay for said slow acting relay, a step-by-step means controlled by said line relay to take one step for each of said impulses in a. series so as to successively close local channel circuits for each step, a bus wire, circuit means including a front contact of said slow acting relay and a back contact of said slow acting repeater relay in multiple for applying energy to said bus wire, circuit means for also applying energy to said bus wire temporarily at the end of a series of impulses and until after said slow acting repeater relay is dropped away, said means being effective only providing said step-by-step means has taken the proper number of steps for that series, pairs of neutral relays for each of said steps, means including said local channel circuits and said line relay rendered effective during particular ones of said series of impulses for energizing one or the other of said.

neutral relays for each step depending upon whether the impulse on said line circuit for that step is positive or negative, stick circuit means for each of said neutral relays including its own front contact and receiving energy from said bus wire, whereby any of said neutral relays picked up during said series of impulses are dropped away at the end of such series unless the proper number of steps has been taken by said step-by-step means, and other circuit means for applying energy to said bus wire at all times except during said particular ones of said series of impulses during which said neutral relays are being controlled over said local channel circuits, whereby said step-by-step means may at times operate without said stick circuits being rendered dependent upon the number of steps taken by said step-bystep means.

18. In a remote control system, a linev circuit having different series of time spaced distinctive impulses selectively applied thereto, a line relay responsive to the distinctive characteristic of each impulse of each of said series, a slow acting relay controlled by said line relay so as to be picked up at the beginning of each said series and dropped at the end of each such series, a slow acting repeater relay for said slow acting relay, a step-by-step means controlled by said line relay to take one step for each of said impulses in a series of impulses so as to successively close local channel circuits for each step, a bus wire, circuit means including a front contact of said slow acting relay and a back contact of said slow acting repeater relay in multiple for applying energy to said bus wire, circuit means for also applying energy to said bus wire at the end of each said series of impulses during the time period between the successive deenergizations of said slow acting relay and said slow acting repeater relay, said means being effective only providing said step-by-step means has taken the proper number of steps, pairs of neutral relays for each of said steps, means including said local channel circuits and said line relay rendered effective during particular ones of said series for energizing one or the other of said neutral relays for each step depending upon the distinctive character of the impulse on said line circuit for that step, stick circuit means for each of said neutral relays including its own front contact and arranged to receive energy from said bus wire, whereby all of said neutral relays picked up during any particular series of impulses are dropped away at the end of such series unless the proper number of steps has been taken by said step-bystep means for that series, and other means for applying energy to said bus wire at all times except during said particular series of impulses during which said neutral relays are being controlled over said local channel circuits, whereby said step-by-step means may at times operate without said stick circuits being rendered dependent upon the number of steps taken by said stepby-step means.

NEIL D. PRESTON. 

